Coal briquette and process of making it



Patented .luly 24.1, 1m28.

U ll 'll if] u all GEORGE ALBERT CHAPMAN, F FOREST HILLS, AND EETOFTWRAY WILKINSON, OF QUEENS VILLAGE, NEWl YORK, ASSIGNORS TO MINERALSSEPARATION NORTH AMERICAN CORPORATION, OF NEW YORK, N. Y., A CORPORATIONOF MARYLAND..

COAL BRIQUETTE AND PROCESS 0E MAKING: IT.

"No Drawing.

This'invention relates to coal.' briquettes and processesof making them,and is herein illustrated in part as applied to the production ofbriquettes from high ash coal and vfrom coal ashes such as are found oncity dumps.

Inthe briquetting methods hither-to used it has usually been `deemednecessary to dry the coal in rotary driers until it contained less than1% of moisture. It has also been deemed necessary to limit thecrushingof the coal to a minimum amount because it has been deemednecessary to keepth'e total sur face of the coal particles as small aspossible, thus reducing the amount of binder required to coat thesurface of the particles Coarse crushing has resulted in retaining in lthe coarse particles much of the ash which would be mechanically freedby fine crushing and could then be separated by suitable methods of coalconcentration. Such processes therefore cannot commercially `convert thehigh-ash waste of coal mines into valuable fuels in competition with thegood coal generally marketed. Usually the hot, dry, coarse-crushed coalas it comes from the drier has been mixed with hot oil or tar orasphaltic binder in a mixer which had to be kept hot. The mixed hotmaterial. has usually been cooled slightly, pressed 1n a briquettc pressand then baked in an oven to set? the binder and drive olf some of thevolatiles from the binder.

The briquettes thus produced from American coals have usually provedunsatisfactory for the, American market. Those containing upwards oft'en per cent of oil or asphalt usually have been quite smoky, whilethose containing smaller amounts of binder have been objectionablebecause the binder has failed to mix uniformly With the coal, some coalparticles having too much binder and others having too little or none atall, resulting in a dusty b1iquette,-tliat isone which goes largely intodust when it breaks, becaust the uncoated particles or insul'lieientlycoated particles have no tendency to stick together. As a result thebriquette loses its integrity in burning and the particles which arepractically unbound fall apart as dust. Iudomestic fires this dust fallsthrough the grates, passing into the ash as unburned carbon, With theresult that the ashes left bv` burning the briquettes hitherto madeApplication 1aed March 1? ,1926. serial no. 95,45el'. l

in dusty briquettes which as above noted are wasteful andunsatisfactory.

According to the present invention these and others objections areovercome. Moreover it is found possible to crush the coal hne and yetuse a relatively small amount of binder. ,The process therefore is Welladapted to produce valuable fuel fromhigh ash Waste coal which can becrushed fand' concentrated as well as fine `Wastecoalyboth of which arenow generally rcgardedas useless, and which gencrallyrhave not beencapable of* p rolitable utilization in commercial briquettmg processeswith lAmerican coals for lthe American market. The coal is usual lycrushed to liner than ten-mesh and frequently even to less thanthirty-five mesh. depending on the quality and ash content of the coal.This fine crushing frees many par ticles of coal from included oradhering ash, and thus facilitates the separation ot' the pure coal fromthe ash by the froth-tlota tion process. l/V'here the coal isconcentrated by froth-flotation there is usually employed in thisprocess a soluble. mineral-frothing agent, such as. cresylic acid, andalso an oil, Which for example, may be a tar oil or coke oven tar ortopped petroleum.

The crushed coal With the flotation agents is agitated in sufficientwater to make a freely flowing pulp with the result that the coalfloats. If little oil has been used the separate coal particles arecarried in bubbles which float in the form of a froth., If largeramounts of oil have been used the coal will become agglomerated and theagglomerates may be floated or may be sunk.

Usually it has been found preferable to concentrate theV coal byfrotli-iotation, `thus enabling the purified coal to be separated fromthe bulk of the pulp by removing the floating coal, thus easily andeconomically separating -the coal from the bulk of the Water of the pulpand from the ash which remains behind in the pulp Water. It may beadvantageous to concentrate the coal by added in the aie Wellagglomerated by an 'agglomerates of f. t0 Vthereafter reducefroth-flotation With a little oil and then add more oil to agglomeratethe coal. 'lhis may reduce the Water associated with the coal from say200% to say 35%.

A large proportion of the oil necessary for binding purposes in theproduction of briquettes is often thus disseminated by agitation in thepresence of Water, thus effecting a uniform distribution of it on thesurface of the coal particles. Usually this extra oil has the advantageof facilitating the draining of the Water away from the coal to bebriquetted. The oil in some cases may be form of emulsion, especiallywith heavy oils, or tars which play the part of oils, and the emulsionmay be made with laundry soap or other emulsifying agent before addingit to the pulp.

lt has been found advantageous to add to the aqueous pulp, in general,not more than about 2% or 5% of oil measured on the Weight of the coal.The rest of the oily or other binding agent is usually mixed later withthe dried or partly dried pulp, as in a paddle or dough mixer. It ispreferable that air or gas be present in th pulp when adding the binderto the pulp or causing the binder to'coat the coal particles in thepulp.

One great advantage of adding a substantial part of the binder in thepulp so that the coal is coated with it by agitation in Water, is thatall of the particles of coal seem to be almost uniformly coated With thebinder and thus, in the presence of sufficient binder, are certain toadhere or stick to each other and produce a practically .dustlessbriquette. Moreover if the coal particles oily material such as oil, taror pitch, the coal'particles and the agglomerates become Water-repellentand Water runs away from the coated coal and from the agglomerates, andis practically free of coal. i

Owing to the fact that the agglomerates are Water-repellent they may bedrained by leaving them in heaps, although it is usually preferable .tedrain them by special draining appliances such for example as a cocoamatting in the form of a continuous belt. Frequently the best resultsare obtained When the agglomerates are drained by means of a continuoussuction or centrifugal filter. Sometimes it is possible to obtain thecoal in the form of hard shotlike granules, especially when theagitation is accompanied by a minimum of aeration. Such shotlikegranules may be freed from Water by centrifuging. The drying operationusually reduces the moisture contained to somewhere between 15% and 25%.It is not found necessary to dry the agglomerates to the extent that hashitherto been deemed necessary in drying the materials for briquetting,but it is usually advantageous the contained moisture,

either by heat or by pressure, to'between 5% and 10%. The moisture maybe expelled by pressing these agglomerates in a mold which is providedWith narrow drainage openings or slots, since the agglomerates usuallydo not flow through such openings under pressures running up to two tonsor more per square inch. The continuous lscrevv press as of the typeused for pressing oil from seeds may be used where large capacity is notrequired. l

To produce astrong briquette from the agglomerates containing from oneto five or sometimes more per cent of oily material, the oil-coated coalparticle or agglomei'ates are preferably mixed with a further quantityof binder, which `may be melted or crushed pitch, or Mexican fuel oil7or any one of a large number of oily materials, or sulphite celluloseliquor residues. It will be noted that these materials are substantiallyashless. Vhen coal particles are already oilcoated, either by thisprocess or in other Ways, there is little difliculty in uniformlycoating them With a further` quantity of oily material. It has beenfound possible to mix in uniformly as littleas two or three per centadditionall oil in a paddle mixer ora dough mixer, either hot or colddepending upon the material, and in this Way add the amount ofadditional oil or oily material necessaryto make good and uniformbriquettes. For reasons of economy the total oil or oily material neededas binder 'to make good briquettes is kept as small as possible. Forvother reasons it has been found advisable to keep the oily materialbelow 10% to 12%, depending on the nature and coarseness of the coal. Ifmore than that amount is used the coal has an oily feel,

and the unbaked briquctte is too soft 0r mushy. v

By properly adjusting the percentage of total binder and the percentageof moisture it has been found possible to obtain oilcoated coalparticles which may be pressed into briquettes such as the ordinarypillowbriquettes that Will not stick in the mold and vwill burn Withoutbreaking, will be dustless, and Will bear handling by the automatlicmachinery used for the handling of coa Usually the briquettes afterbeing formed in the molds are too soft to bear such han- (lling, ing ata temperature high enough to drive ofi some of the volatiles from theoil or other binder and yet not high enough to actually have the effectof producing coke. rIlhis renso they are usually hardened by bakders thebriquettes smokeless -and odorless,

thus fitting them foi' sale in the most exactingmarkets. ally obtainedby baking at temperatures above 300o F. and ultimately reaching aboutThese results have been usu- 500o F., but, generally, not much exceeding13p the latter ligure, although with some oils temperatures ultimatelyreaching 650O F. for a short time have been found to be mostsatisfactory. The baking of pillow-briquettes reaching a thickness of aninch and a quarter has usually required one and one-half to two hours atthe temperatures named.

Single briquettes would sustain a crushing weight of 125 pounds whenproperly made.

lt is found that briquettes of fine coal made as above described bearrough handling and burn better than do similar briquettes made ofcoarser coal. 'It has been found that a properly made domestic fire ofsuch fine coal pillow-briquettes will burn for twenty-four hours Withoutapparentv Ydiminutionv of volume if left undisturbed,

i ous structure of the ash is such that air passes through it and burnsout the carbon of the coal so that the ashv of briquettes burned inordinary domestic; 'stoves contained as little or two to three per centof unburned carbon.

lt was found that the different oily materials lost different amountswhen` the briquettes were baked and that relatively larger. amounts ofoily materials had to be used as binder where their volatile content washigh. @ne sample of Mexican fuel oil lost 45% on baking'.

It was found that some coals, and particularly the coal contained in theashes of a city ash dump, did not take up enough oil or oily binder toform satisfactory agglomerates when agitated with the oil or oily binderin an aqueous pulp. It was found however that very good agglomeratescould be made from such coals by adding a small amount, say one to threeper cent of oil or oily binder in the aqueous pulpf The further binderneeded to make the, briquettes was added by mixing in the additionalbinder with `the fairly well dried agglomerates after removal .from thepulp.

In recovering coal from the. ashes of a New York city dump it was foundthat 25% to 30% of the ashes were fines which passed through 28 meshscreen and that these fines contained only a few per vcent of coal.Accordingly in most runs the finespwere separated and rejected beforegrinding the ashes to 20 to 35 mesh preparatory tocon centration. l

Example 1.-Ashes from a New York city ash dump screened and ground asabove were suhjectedto froth-flotation treatment `with a suit-ablesoluble frothing agent and with oily material, and then further oilymaterial was added until about four or live 'per cent ofoily material onthe coal present had been added. The partly drained Wet concentratecointained abouti-32% of water. To 125 pounds of this concentrate(estimated to contain 100 pounds of solids) 'were added three pounds offinely ground pitch, and the whole mixture was put through an AndersoneXpeller to reduce the water content to approximately ten per cent. Thedischarge from the Anderson expeller was further mixed and thenbriquetted. The resulting briquettes were baked at a suitabletemperature to make them practically smokeless. rlhe nished briquettes,after cooling, were tested as to Atheir water absorbing quality byimmersion in water for about twenty hours,V and it was found that theyabsorbed only from ll/2% to. 6% of water. l

Similar concentrates were agitated in a .pulp in a standard mineralsseparation machine with between 41% and (i1/2% of gas house coal tar toform agglomerates. These wereseparated from muchof the pulp water, byflotation, drained on burlap to further reduce the water to' 32.8%, andthen put through an Anderson expeller to reduce the water to 9%. Theresulting cake was fed directly to a Belgian roll briquettingmachinehand the resulting briquettes baked for one and one-half hours atabout 500o F. The resulting briquettes were excellent. After coolingthey were tested by immersion in water for twenty hours and it was foundthey had absorbed from 1.7% to 1.9% water and showed no signs ofdisintegrating and were hard.

No determinations of ash content: were made during this run, but suchdeterminations were made in connection with another V substantiallysimilar run in which the ashes were passed over a sixteen-mesh screen tosepara-te out the lines. The material retained on the sixteen meshscreen was fed to a standard ball mill to be ground for fio'-v tationfeed. The fine material was passed through a Dori' classifier adjustedso that the overflow carried about .two per cent of material largersthan35 mesh. This overliow constitutedtlie mill tailings. The coarsematerial from the classifier passed to the ball mill along with thecoarse material from the sixteen-mesh screen and constituted thellotation feed. The flotation feed was ground in the ball mill so that82% of it passed a hmesh screen and this contained 67.5% of as Thedotation `was effected in a series of six minerals separationpositive-feed subaeration vessels. The feed to flotation averaged abouta .ton and a half of, solids per hour. To the material in the ball millwas i material fed to the mill.

added an emulsion of Mexican. fuel oil and Water containing of oil and afraction of a per cent of laundry soap so .that thev oil fed amounted to22.8 pounds per hour, together with about 1.1 pounds of crosylic acidper hour. A further 0.4 pound of cresylic acid per hour was fed to thefirst agitating vessel. The froth. overflow from this vessel was fed tothe fifth vessel in the serieswhich, together with the sixth vessel,retreated the froth overflow.. The. tailings from the. first vesselpassed successively through the second, third and fourth vessels and thefioat therefrom was returned to the first vessel. The tailings from thesixth vessel were returned to and divided between the second and thirdVessels. Together With them was fed the overflow from the thickener inwhich the concentrate obtained from the fifth and sixth vessels wasthickened. The flotation tailings from the fourth vessel werercturned tothe mill feed so that they passed through the sixteenmeshscreen andthereafter were treated as part of the raw The finished' concentratecoming from the thickener contained 15% ash, which .was reduced by filtration to 13%.

Eau/malle 2.-A high ash coal from St. Clair Coal Company, St. Clair,Pennsylvania,'\vas ground in a ball mill so that all but 1.2% passedtwenty mesh and 52.2% passed one hundred mesh. This was fed at the rateof from three-fourths of a ton to 'a tonrv and a h alf per hour to aminerals separation positive-feed subaeration machine of six cells. Inthe froth-flotation concentrating operation coal tar was added to theaqueous pulp at the rate of 7.6 pounds per hour together' with pine oilat the rate of one quarter pound per hour, oxidized petroleum at therate of 4.5 pounds per hour, cresylic acid at the rate of 3.6 pounds perhour, and a Mexican fuel oil emulsion containing about one third Waterand a very little soap, 1.47 pounds per hour. The original ash content iof the/coal, 27.5%, was reduced in the conyce centrate to 14.75%. Thisconcentrate. was agitated in a minerals separation standard machine andcoke oven coal tar Was added at the rate of 61.8 pounds per hour to formagglome-rates. The agglomerates were overfloived and after filtrationcontained from 13.5% to 17.5% of water and Were further dewatercd bypassing them through an Anderson expeller and the product Was then mixedin a C. P. Day Company dough mixer with rather more than five per cent(com-4 puted on the coal present) of coke oven tar. to make a totalestimated binder of about nine per cent on the coal present in' theagglomerates. The resulting material Was made into briquettcs which werebaked aty a suitable temperature. Tested in a standard type of domesticgrate they V4Were found to be smokeless, they burned Well, and theyretained their shape during burning. The resulting ashes contained anaverage of two totwo and one-half per cent of unburned carbon ascontrasted with unburned carbon contained in the ashes of briquettesproduced by prior art processes of about 50%.

Eample 3.-High ash coa-l sludge from the Philadelphia and Reading Coaland Iron Company containing 27.75% of ash Was fed to a standard typeball mill together With an emulsion containing Mexican fuel oil and alittle laundry soap so that the oil fed amounted to 13 pounds per ton.With this material which was about 35 mesh or finer was fed 2.8 poundsof cresylic acid per ton so that there was a total feed of agents Withthe coal amounting to' about 15.8 pounds per ton of material fed. Frothfiotation Waseffected in a minerals separation `positive-feedsubaeration machine having eight cells. There Was added at the firstcell an additional 1.05 pounds of cresylic acid per ton of solids in thefeed. The concentrate from the first two eellswas fed to the seventhcell which, Atogether With the eighth cell, was used as a cleaner. Thetailings from the second cell passed through the third, fourth,

flotation tails, while the overflow from these latter cells was returnedas middlings to the feed atthe first cell. An additionaly 0.25 pound oferesylic acid per ton of solids in the feed was added at the fifth cell.The over flow from the eighth cell,\ constituted a cleaned concentrate.The concentrates were heaped up, the product of several similar runsbeing mixed together.

The ash content averaged about 11.0%. These were dried to about 7% ofWater and mixed in a dough mixer with additional 9% of Mexican fuel oiland then made into pillow briquettes in a set of 4-pocket Mashekbriquetting rolls (Belgian type). The briquettes did not stick to the`rolls and there wasl very little breakage of them. The briquettes werebaked `for one hour and a half at a temperature rising to something over500o F.. This yielded excellent briquettes which burned with so littlesmoke that it was not noticeable except upon careful examination.

Having thus described the invention,`what is claimed is:

1. A baked briquette consisting of uncoked anthracite coal substantiallypassing 10 mesh and bound by a. binder which consists largely oftheresidue of oil which is less then ten per cent on the coal, saidbriquette being adapted when burned in a deep mass in a grate to leavean ash containing less than ten per cent of unconsumed carbon andl of'uncoked line anthracite coal bound together b y a substantially ashlessbinder which is less than ten per cent on the coal,

- said briquette being substantially free ol dust than ten per cent onthe coal, said briqucttebeing'substantially free of dust when broken andburnahlc in a gratewithout substantial softening so as to leave an ashcontaining less than ten per cent of iinconstuned carbon.

4l. A strong coal baked briquctte consisting o'l' uncoked anthracitecoal passing l0 mesh bound together by4 a binder which consists largelyot' the residue of banked oil which is less than ten per cent on thccoal, said briquette being burnable in a grate Without substantialsoftening so as to leave an ash containing less t-han ten per -cent otunconsuined carbon, and absorbing less than seven per cent of its Weightof Water upon prolonged immersion in water.

5. The process of making coal briquettes which consists in treatingline. coal to coat it With a substantially uniform coating consistingoi' oily mate-rial in too small amount to serve as a binder, and thenmixing the oilcoated coal, with further substantially ashless binder,and forming it into briquettes.

G. The process of making coal briquettes which consists in agitating anaqueous pulp ot line coal with an oily reagent to produce oil-coatedcoal agglomerates, separating the agglomerates from the pulp and fromexcess Water, mixing with -furthe-r oily substantially ashlcss binder,and forming it into briquettes.

7. rlhe process ci making coal briquettes which consists in agitating anaqueous pulp oii'the impure coal with a mineral-trothing agent and withan oily reagent to produce oil-coated coal particles, separating theparticles from thenpulp and. lrom excess Water, mixing with furthersubstantially ashless binding material, and forming it into briquettcs.I

S. llhe process of making coal briqucttes which consists in agitat-ingan aqueous pulp ol impure coal with a miueral-'trothing 'agent and withan oily reagent to produce floating A l'oil-coated coal agglomeraties,separating the agglomcrates from the pulp and from excess Water, mixingwith further substantially ashless binder, and forming it'. intobriquettes.

0. The process ot' making coal briquettes Which consists in agitating anaqueous pulp of fine coal with an oily reagent to produce oil-coatedcoal particles, separating the,particles from the pulp and from excessWater,

mixing with further substantially ashless binding material, forming thebriquettes, and baking the briqucttes at a tempera-ture reaching theneighborhood of ()O F.

l0. lhe process ot making coal briquettes which consists in agitating anaqueous pulp of the impure coal with a mineral-frothing agent andfwithan oily reagent to produce floating oil-coated coal particles,separating the iiarticlcs from the pulp and `from excess Water and itscontained ash, mixing With further substantially ashless bindinginaterial, and forming it into briquettes.

ll. 'lhc process ot making coal briquettcs which consists in agitatingan aqueous pulp of the impure coal with a mineral-frothing agent andwith an oily reagent to produce floating oil-coated coal particles,separating the particles from the pulp and from. excess water and itscontained ash, 'mixing with Jfurther substantially ashless bindinginatcrial, forming the briquettesand baking thc briquettes at atemperature reaching the neighborhood oi2 50() o F. v

l2. rlhe process of making coal briquettes which consists .in agitatinga pulp of the lcoal with an oily reagent adapted to serve as binder toproduce float-ing agglomerates, overl'lowing the agglomerates from thepulp to separate them from .most of the excess Water', furthervdewatering the agglomeratcs, mixing the agglomeratcs with furtherbind.- er, and then forming the mixture into briquettes.

13. .The process of making briquettes from impure coal which consists inagitating a pulp of the impure coal With a mineralfrothing agent toproduce a. floating coal concentrate, agitating the coal concentratelwith an oily reagent adapted to serve as binder to produce floatingagglomerates, overflowing the aggloinerates from the pulp to separatethem from most of the excess Water, further dewatering the agglomerates,mixing the agglomerates with further binder, forming the mixture intobriquettes, and baking the briquettes. y

la. The process of making coal briquettes which consists in agitating,an aqueous pulp ot impure coal With a mineral-frothing agent to producea floating concentrate supported by bubbles, adding oily material whichis adapted/"to serve as a binder, and further agit-ating to produceagglomerates of oil-coated coal, removing from the agglomerates theexcess Water, mixing further binder with the relatively dryagglomerates',l molding the briquettes, and baking the briquettes.v f

l5. The process of making coal briquettes which consists in agitating anaqueous pulp of impure coal with a mincral-frothing agent to produce afloating concentrate supported by bubbles, adding oily material which isadapted to serve as a binder, and

further4 agitating to produce agglomerates of oil-coated coal, removingfrom the agglomerates the excess Water, mixing further oily binder withthe relatively dry agglom-v as a binder, and further agitating toproduce agglomeraties ofoil-coated coal, removing from the agglomeratesthe excess Water, mixing further binder with the relatively dryagglomerates, `molding the briquettes, and baking the briquettes. I

17. The process of Vmaking coal briquettes which consists in agitatingan aqueous pulp of impure coal with a mineral-frothing agent and with anoil to produce a fioating concentrate supported by bubbles, adding moreoily material which is adapted to serve as a binder, and furtheragitating to produce agglomerates of oilcoated coal, removing from theagglomerates the excess-water, mixing further oily binder with therelatively dry agglomerates,v molding the briquettes, and baking thebriquettes.

18. The process of making coal briquettes .from ashes Which consists inseparating out the finer ashes, grinding the coarser ashes to free coalparticles from adherent ash, agitating an aqueous pulp of the groundashes ticles, separating the float from the pulpA and `vfrom excessWater and its contained ash, mixing with further substantially ashlessbinding material, forming the mixture into briquettes and baking them toproduce almost or absolutely smokeless briquettes.

19. The process of making coal briquettes from ashes which consists inseparating out the finer ashes, grinding the coarser ashes to free coalparticles from adherent ash, agi- .tating an aqueous pulp of the groundashes with a mineral-frothing agent and with an oily agent to producefloating oil-coated particles, separating the fioat from the pulp andfrom excess Water and its contained ash, mixing with furthersubstantially ashless oily` binding material, forming the' mixture intobriquettes and baking them to produce almost or absolutely smokelessbriquettes.

In testimony Whereoiwe have alixed our signatures to this.specification.

GEGRGE ALBERT CHAPMAN. ELTOFT WRAY VILKINSON.

